Section 2. Review of Literature

This section contains a summary of the available literature related to incident
management, and performance measures for incident management systems. It should
be mentioned that there is very little literature from the law enforcement/emergency
service providers' perspective directly related to transportation-related
incident management and performance measures. Most of the information presented
here for the emergency services perspective was derived or inferred from a
limited number of references.

What Is an Incident?

Transportation Perspective

One big issue that has to resolved before incident management performance
measures can be developed is what, exactly, is an incident. Transportation
providers and emergency responders tend to have different definitions for
what constitutes an incident. This is primarily because of the different missions
that transportation and emergency service providers have in many areas.

Even within the transportation literature, transportation agencies and officials
tend to define incidents differently. The Traffic Incident Management
Handbook [1]
defines an incident as "any non-recurring event that causes a reduction
of roadway capacity or an abnormal increase in demand." Under this definition,
events such as traffic crashes, disabled vehicles, spilled cargo, highway
maintenance and reconstruction projects, and special non-emergency events
(e.g., ball games, concerts, or any other event that significantly affects
roadway operations) are classified as an incident. The Traffic Management
Data Dictionary (TMDD), as published by ITE and AASHTO, defines an incident
as "an unplanned randomly occurring traffic event that adversely effects
normal traffic operations." [3]
Developers of the TMDD distinguish incident conditions from planned activities,
such as roadwork or maintenance activities by defining different data elements
and message sets for both incident and planned roadway events. The 2000
Highway Capacity Manual [4]
defines an incident as being "any occurrence on a roadway that impedes
normal traffic flow." While these definitions are very similar, they
tend to suggest that within the transportation community, different officials
tend to define incidents slightly differently. This can lead to confusion
when dealing across jurisdictional boundaries and in reporting and interpreting
incident management performance measures.

Emergency Services Perspective

While there are no real clear-cut definitions of an incident, most law enforcement
agency and emergency responders seem to define an "incident" as
any event to which they are dispatched or requires a "response"
or action by them. Generally, law enforcement and emergency responders view
their mission as "public safety" and "prevention of loss of
life and property." Therefore, these agencies are driven to respond
to events that might be perceived as having an impact on the public safety
or the potential of loss of life. Major events, such as vehicle collisions,
overturned vehicles, vehicle fire, would all be classified as an incident
by both law enforcement and emergency responders because the nature of these
events generally requires them to respond. Less critical events, such as stalled
vehicles on the shoulder, debris in the roadway, etc., may not be considered
an "incident" in many locations because an action or response
would not be required from a law enforcement and emergency response perspective.
For example, fire departments generally do not classify stalled vehicles or
debris in the roadway as an "incident" because they do not generally
respond to those types of events. Again, this varies from location to location.

It should also be noted that the definition of an incident by law enforcement
and emergency responders includes more than just events effecting traffic.
Potential suicides, structure fires, criminal activities, and other events
off the roadway are considered to be "incidents" by law enforcement
and emergency responders because these events require a response from these
agencies.

The definition of an incident also appears to be highly dependent upon the
type of dispatching arrangements and structure of the emergency response agencies
in an area. For example, in Dallas, the fire and police departments use a
common 911 dispatching center. If a call comes into the dispatching center
requesting both a fire and police response, both are dispatched to the scene,
even though there may not be a true need for both responses. The fire unit
arriving on the scene then makes the determination if their presence is truly
needed. Because they have been asked to respond to the scene, the fire department
would generally classify this as an incident because their equipment is in
a response mode and is unavailable to respond to another event.

Because law enforcement vehicles can patrol sections of roadways, they may
occasionally "happen" upon an incident scene (such as a stalled
vehicle in a travel lane) and "respond" to that event without
being dispatched. The decision as to whether or not classify this type of
event as an incident seems to depend upon whether or not the event is a public
safety concern requiring a response. For example, a stalled vehicle blocking
a lane of traffic is generally viewed as a public safety issue because of
the potential of the vehicle causing a secondary crash, and would generally
be classified as an incident. Some law enforcement agencies may not necessarily
classify a stalled vehicle on the shoulder as an "incident" requiring
their response because it may not be viewed as mission critical and may not
necessarily represent a public safety concern.

Classification of Incidents

Transportation Perspective

From a transportation perspective, incidents tend to be classified based
upon their impact on traffic operations. Many transportation agencies have
devised ranking systems for classifying incidents to assist in determining
the appropriate level of responses. For example, the Chattanooga Urban Area
Metropolitan Planning Organization and the Chattanooga-Hamilton County Regional
Planning Agency have devised a classification system that is based on traffic
flow, impact/delay, incident characteristics and types of responders. [7]
A Level 4 incident is one that typically is causing traffic delays of less
than 30 minutes where traffic is only slightly impacted and can be relatively
easily routed around the incident. A Level 3 incident is one lasting more
than 30 minutes but less than an hour, and a moderate impact on traffic flow.
Typically a Level 3 incident involves a collision without or just minor injuries.
A Level 2 incident is one lasting more than 30 minutes, but less than 2 hours.
In a Level 2 incident, the impacts on the flow of traffic are significant,
and the incident probably involves injuries to motorists. With a Level 2 incident,
traffic management is essential and site management involves significant interagency
cooperation. A Level 1 incident generally tends to be major events that close
the roadway and cause major area-wide congestion.

Many other areas use similar classification systems to help agencies define
the appropriate level of response in the region.

Emergency Services Perspective

While most transportation agencies tend to classify incidents based upon
their impact on traffic operations, law enforcement and emergency response
agencies tend to classify an incident on the number and severity of potential
injuries and the number of apparatus required to affect an adequate response.
Radio dispatching codes were used to gain insight into the way that different
law enforcement and emergency providers classify incidents (see Appendix
A for example of select radio codes). For the most part, because their
level of responsibility varies from investigating potential criminal activities
to maintaining law and order, law enforcement agencies generally tend to have
more categories for classifying incidents than fire and emergency service
responders.

Appendix A contains the model dispatching codes
developed by the Association of Public-Safety Communications Officers (APCO).
[15] Of the approximately
100 dispatch codes, 14 are related to transportation events. Ten of the 14
are used to describe different incident-related type of responses. Most police
agencies use fewer numbers of dispatching codes that are used to describe
or classify different incident situations.

Fire and emergency medical services generally use criteria that alert them
to the number and type of apparatus that are going to be dispatched and the
potential for loss of life. Dispatching codes for the New York City Fire Department
are also shown in Appendix A. Relatively few
dispatching codes (a total of 4) are used to describe traffic incidents.

Performance Measures

Transportation Perspective

Many transportation agencies do periodical assessments of their incident
management systems. The Traffic Incident Management Handbook [1]
reports that the most commonly used statistics in evaluating incident management
programs include the following:

The number of service patrol assists;

The average elapsed time from incident occurrence to detection;

The average elapsed time from the point at which the incident response
team is called out until its arrival on-scene; and

The average elapsed time to normal traffic flow restoration.

In May 2000, State Highway Administration of Maryland and the University
of Maryland produced Performance Evaluation of CHART "An Incident
Management Program" in 1997. [5]
The purpose of the evaluation was to "assess the effectiveness of the
Maryland CHART program with an emphasis on its ability to detect and respond
to incidents on major freeways and highways" and to assess "the
efficiency of the entire incident management operations along with its resulting
benefits." The evaluation examined issues such as detection time, response
travel time, clearance time, response time, and incident duration. The operational
definitions used in the evaluation included the following:

Detection Time – the elapse time between when an incident
occurs to when it is detected

Preparation Time – the elapse time between when an incident
is detected to when the response vehicles are dispatched.

Response Travel Time – the elapse time between when the
response vehicle was dispatched and when response vehicles arrive at the
incident scene.

Clearance Time – the elapse time between when response
vehicles arrive at the incident scene to when traffic completely recovers
after the incident.

Response Time – the elapse time between when an incident
is detected to when the response vehicles arrive at the scene.

Incident Duration – the elapse time between when an incident
occurred to when the response vehicles depart at the scene.

The report went on to present an analysis of incident characteristics. The
researchers used 12 months of incident reports from all three of the traffic
operations centers and accident report data from state police for completing
this analysis. The researchers use these records to examine the distribution
of incidents by the following:

Roadway;

Blockage duration;

Peak and off-peak hours;

Weekday and weekend;

Lane blockage; and

Location (exit ramp numbers).

The researchers indicate that this information can be used to better design
incident management strategies, such as the distribution of patrol vehicles
around freeway segments of a high incident frequency; assessing the impact
of areas under the average and the worst incident scenarios, and identifying
hazardous highway segments from both the safety and operations perspectives.

Using the incident data, the researchers also evaluated the effectiveness
and efficiency of their incident detection system. The researchers used two
primary measures of effectiveness in this evaluation:

Incident response rate

Distribution of detection sources

For this evaluation, the researchers defined the incident response rate to
be "the ratio between the total number of traffic incidents reported
to the CHART control center and those managed by the CHART incident response
team." Not surprisingly, the researchers reported response rates at
the three TMCs to be 99%, 94.7%, and 92.3%. The researcher noted that no reasons
were given in those incidents when the incident team did not respond. The
researchers recommended that CHART operators "should clearly document
such incident scenarios, and detail the reasons for those incidents to be
handled by police alone." In discussions with the CHART operators, the
researchers found that in some of those incidents, the response team was unable
to respond because of "equipment limitations or manpower shortage."

The researchers also conducted an analysis of incident response efficiency
specifically addressing the following:

The time it took for an incident response unit to reach the reported incident
site after the control center was informed

The average travel distance for incident response units to reach the identified
incident site.

The approximate reduction in the incident blockage time due to the operations
of CHART's incident response program.

As noted above, the researchers defined response time as the "elapsed
duration from the moment the control center received a reported incident to
the physical presence of the incident management team at the target incident
site."

In looking at the reduction in incident duration, the researchers noted that
there are two ways of doing this. The first way is to perform a "before
and after" comparison where response times to incidents before and after
the system is operational. The researchers rightfully noted that in most locations,
incident response time data prior to actual operations of a center is sparse,
at best. They suggested that another way to examine the reduction in incident
duration is to compare incident durations when the incident management team
responded to incident durations when the incident management team did not
respond. One drawback to this, however, is that data from when no response
occurred may be limited in many centers.

The report included information estimating benefits of incident management
system. The researchers indicated that "despite well perceived benefits
from an efficient incident management system, most state highway agencies,
including MSHA, are facing the pressing need to justify their system investment
and operating costs, especially in view of diminishing resources and increasing
demand for infrastructure renovation." The researchers indicated "to
ensure the quality of analysis under the data limitations as well as resource
constraints, the benefit assessment of CHART was focused only on those [measures]
either directly measurable or quantifiable from the given data." Therefore,
the researcher focused on the following performance measures:

The number of assistance request from drivers;

The reduction in secondary incidents;

The reduction in driver delay time;

The reduction in vehicle operating hours;

The reduction in fuel consumption; and

The reduction in vehicle emissions.

In their analysis, the researchers defined assistance requests as an event
where the driver asked for assistance such as flat tire, shortage of gas,
or some mechanical problem. The researchers noted that "according to
CHART staff, its response teams actually responded to many more assistance
requests from drivers" than was used in the analysis, but because "most
of the unreported driver assistance [requests] did not need major efforts
or equipment from the response unit," no data were recorded on these
events. This suggests several issues that must be addressed in assessing the
performance of incident management systems:

It is important to define the measures that are going to be used to evaluate
the performance of the system PRIOR to analysis period so you know what
data to collect.

It is important to have the mechanisms in place to ensure that all the
data that will be used to evaluate your system is collected.

The researchers also used the reduction in the number of secondary incidents
in their assessment of the benefits of the CHART system. For the purposes
of their evaluation, the researchers defined "secondary incidents"
to be "any incidents occurring within two hours after a major incident and
within a two mile range of a reported incident." In looking at the "reduction
in secondary incidents," the researchers estimated the number of secondary
incident without CHART by factoring up the number of observed number of incidents
by the percent reduction in average incident duration. The researchers used
simulation to quantify the reductions in driver delay, fuel consumption, and
vehicle emissions.

While some agencies undertake performance assessments similar to that performed
for the CHART system (i.e. a before-and-after comparison performed by an outside
agency), other agencies produce performance reports on a more routine basis.
For example, the Minnesota Department of Transportation (MnDOT) routinely
produces performance reports that summarize the performance of their incident
management system on a daily, monthly, or annual basis. [9]
Samples of these reports are contained in Appendix
B. These reports generally contain information on the following:

The number and type of incident occurring;

The number and type of vehicle involved;

The number of times different agencies responded to incidents; and

The average response times by each responding agency.

Many agencies that have freeway service patrols or motorist assistance programs
routinely produce performance reports. [11, 12]. Generally,
these reports include information on the following:

The number of assists performed annually, quarterly, or per month,

The types of assists encountered,

The types of services rendered,

The time of the assists (e.g., Morning, Afternoon, Evening)

The average duration of assists.

Sample reports from the motorist assistance program in Houston, TX are shown
in Appendix C.

Emergency Services Perspective

In many respects, emergency service providers are much more cognizant of
the benefits of performance measures. Many emergency service providers routinely
monitor and produce reports that show their average response times. Historically,
emergency service providers have used response times for justifying adding
new equipment and staffing, and for strategic planning purposes (such as determining
when new fire stations need to be added and where, etc.).

For example, the City of Austin Fire Department has a web site in which they
report their average response times for each month. [13] Response times are
summarized separately based on calls that come into the fire department dispatch
and calls that go into the 911 dispatch center. In producing these reports,
the City defines response time as the time "from the moment a call is
received by the Fire Department Dispatch [or the 911 center] to the moment
when an engine or truck company arrives on the scene." The definition
of response time used by the Fire Department seems to the representative of
most emergency response systems.

Collection and Storage of Incident Management Data

Transportation Perspective

Many locales use their freeway management system software as the primary
means of collecting and storing information about incidents on the freeway
networks. Through various input screens, information about incidents is entered
either by the operator or, at some locations, automatically by the system
itself. The general type of information logged by most systems included the
following:

The roadway on which the incident occurred;

The location (cross-street, mile point, or incident reference system)
of the incident;

Another source of incident information is motorist assistance or service
patrol logs. These logs are kept either by the responding officer in the field
or by the dispatcher located in the control center. These logs generally contain
the same information as the incident management software system, but are collected
by the response individual. In most locations, service patrols are responsible
for responding to minor incidents (such as stalled vehicles); therefore, the
patrol logs are used more to keep track of what resources (such as fuel, etc.)
are used in a response rather than as a mechanism for measuring performance
such as response times, and response durations. Figure 2, which shows the
type of information logged in a service patrol in Ohio, serves as a typical
example of the type of information collected by most service patrol systems.

Emergency Services Perspective

Many law enforcement and emergency service providers (either through their
combined E911 dispatching centers or through their own dispatching centers)
use Computer-Aided Dispatching (CAD) systems. According to Dispatch Monthly
Magazine [16], 56% of local police departments with their own communication
center and 70% of the sheriff departments with their own communications center
use CAD to assist them in their dispatching. The numbers grow considerably
when 911 and E911 dispatching centers are also incorporated. CAD systems were
originally intended to speed-up the process of dispatching roving patrol officers
to a scene; thus, reducing response time. However, these systems generally
have the capability for logging and storing large quantities of data that
can be used to develop response performance measures.

There are literally hundreds of different types of CAD software systems available
on the market, but they generally log similar types of information about responses
— most notably, the time that a request for assistance (or call) was
entered in the dispatching system, the time response was dispatched, the time
the response arrived on the scene, and the time the response vehicle "cleared"
the call (or was available to receive another call). Some CAD systems have
been integrated with automatic vehicle locating systems so that the location
of vehicles is constantly monitored and event times such as vehicle arrival
times and vehicle clear times are logged automatically by the CAD system.
Figure 3 shows a screen capture of one version of a CAD system and illustrates
the type of information that is captured in most CAD systems.

The U.S. Fire Administration (USFA), part of the Federal Emergency Management
Agency (FEMA), maintains a National Fire Data Center (NFDC) that collects,
analyzes, and publishes statistical information about fires and fire responses.
To gather this information, the NFDC established the National Fire Incident
Reporting System (NFIRS). [18]
Participating local fire departments fill out an Incident and Casualty
Report as the fires occur. They then forward the completed forms to their
state office where the data are validated and consolidated into a single database.
A blank Incident and Casualty Report form is shown in Figure 4.

One function of the Incident and Casualty Report is to serve as
a model for the type of records that fire departments around the country should
keep. [18] The
type of data collected for each fire response includes the following:

The day, date, and time of each fire event,

The type of situation found when the responders arrived on the scene,

The type of actions taken upon arrival (i.e., extinguished fire, provided
first aid, etc.)

The type of property involved (including automobiles),

The source or cause of the fire,

Information about the property (address, owner, etc.), and

Information about the type of response provided (i.e., number and type
of responders).

Several fields on this form illustrate the type of data that many fire and
emergency medical service providers routinely collect. These fields are the
Alarm Time, the Arrival Time, and the Time in Service. Each of these data
entry fields are described as follows:

Alarm Time — This is the exact time of day (hour
and minute) when an alarm is received by a fire department alarm center.
It is important for three reasons: (1) as a legal requirement for
recording the precise time of an incident, (2) as information for determining
the frequency of particular types of incidents by time period, and (3) as
the starting time for going into action on an incident, which can be compared
with Arrival Time to determine the length of time necessary
to arrive at an incident [transportation agencies typically think of this
as "Response Time"] and Time In Service to
determine the total amount of time spent at the incident.

Arrival Time — This is the actual clock time when
the first responding units arrive at the incident scene. This time is valuable
to department management because it reflects the actual time spent in traveling
to the scene of the incident. It is useful in determining the actual time
spent at an incident and would indicate any delay between alarm and arrival.

Time In Service — Although each fire department
generally has their own operational definition for "time in service,"
it is usually defined as the time when all or most of the equipment is again
ready for response to another alarm, as determined by the officer in charge
at the scene. This entry is generally in 24-hour clock time and is necessary
along with Arrival Time for calculating the total time
spend on an incident.

Several law enforcement agencies (Kansas, and Houston HPD) that participated
in the survey indicated that their primary means of collecting information
about an incident was the standard accident investigation form. A sample accident
investigation form used in Kansas is shown in Figure 5. Generally, these forms
have fields where officers can fill-in when the accident occurred, when they
were notified, and when they arrived on the scene (see upper right-hand quadrant
of the form). Notice, however, there is not a field to indicate when the officer
left the scene.

Standard Operating Procedures

Transportation Perspective

Many agencies have developed Incident Management Response Manuals. [7,
19] These manuals
define the roles and responsibilities of agencies when responding to incidents,
outline the general procedures to follow when responding to and clearing incidents,
and identify the available resources and capabilities of each agency. These
manuals are generally developed using input from both transportation agencies
and emergency response providers. Some of the special items included in many
of these manuals include the following:

Goals and objectives of the incident management program,

A listing of the agencies involved in incident management in an area,

General procedures for responding to incidents

Procedures for responding to incidents, including

Traffic control requirements,

Detour routes,

Use of emergency lights by response vehicles,

Parking of emergency vehicles at the scene,

Staging of incident responses,

Establishment of command posts,

Procedures for removing disabled vehicles,

Procedures for handling hazardous materials,

Procedures for investigating fatalities and felony incidents,

Procedures for notifying the public about incidents,

Use of video surveillance cameras,

Listing of contacts within response agencies,

Listing of available equipment and resources within each response agency.

Emergency Services Perspective

The U.S. Fire Administration (USFA) has published a Guide To Developing
Effective Standard Operating Procedures for Fire and EMS Departments.
[10] The guide is designed to "assist emergency service managers in establishing
effective standard operating procedures (SOPs)" that "clearly spell
out what is expected and required of personnel during emergency response and
non-emergency activities." This guide specifically states that the standard
operating procedures should not tell firefighters how to do their jobs (i.e.,
technical skills) but describe a department's rules for doing a job (i.e.,
procedural guidelines). It suggests that one important item that should be
included in an agency's SOP is how responders should operate on the roadway.
While the guide does not provide any specific recommendations on how to do
it, it does recommend to fire departments that the SOP cover such items as
the following:

Operations near moving traffic,

Traffic control procedures,

Use of warning devices,

Vehicle/scene stabilization,

Coordination with law enforcement personnel,

Standard procedures and precautions, and

Special situations (e.g., downed power lines)

USFA has also produced a Hazardous Materials Guide for First Responders [8],
which provides a generalized approached for handling hazardous material spills
and incidents. The guide gives first responders information about how to approach
a potential hazardous material spill, what to look for, where to set up command
posts, where to park vehicles, etc. It also provides information on regulatory
considerations, training, and operations in and around hazardous material
spills.

Neither of these guides contain information on what performance measures
fire and emergency response system should be computing or how.